306 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
foundations and 230 on foundations of brick, and in each case 26 per cent moved. Out 
of the total of 455 concrete and brick foundations, 32 per cent were cracked, as follows: 
23 per cent of the concrete foundations were cracked, while 41 per cent of the brick 
foundations were cracked. Nor does this proportion fully represent the facts, for it 
was only in rare cases that the cracking of the concrete was of much importance; while, 
on the other hand, the damage to the brick foundations was often sufficient to endanger 
the stability of the house. The wooden foundations were rarely damaged. In cases where 
houses had especially heavy foundations, the damage was noticeably slighter. Heavy 
concrete foundations rendered structures almost immune to the shock. Not many 
heavy concrete bridges, for instance, were harmed. In a store that rests on the massive 
concrete foundation of a bridge crossing the creek in San Mateo, absolutely nothing 
was disturbed, altho the building overhung the creek about 7 feet. None of the many 
loose articles on the shelves fell, and a high top-heavy machine stood perfectly. 
The falling of brick chimneys suggests the possible influence of the foundations upon 
these structures. Of all the chimneys on houses having wood foundations, 91 per cent 
fell; of those on houses with concrete foundations, 81 per cent fell; of those on houses 
with brick foundations, 88 per cent fell. A truer relation is given by taking merely 
those on the flat land at San Mateo and Redwood City, where the cases are strictly com- 
parable. Of these the proportions in the same order are 93 per cent, 98 per cent, and 
96 per cent. The disadvantage of brick foundations is further attested by the greater 
damage to plaster in houses built on them. 
Brick chimneys. — In the region studied, the tops of 88 per cent of all the brick chim- 
neys fell at the time of the earthquake. This proportion is for the whole region. The 
varying proportions in the different localities are shown in the following table: 
Table showing the number of brick chimneys examined, with per cent which fell, from houses on 
various foundations. 







BELMONT, BURLINGAME 
San MATEO. Repwoop Ciry. | Homestrap, AND | AND SAN MATrKo Toran, 
CARLOs. His, 
Charact f n mn Spe n n on n - n Dey n 3 
foundaiiona: pad Ms 2D > 2 oe 2 Be Ps Be 3 m! 2 
a4 a. a-d a a.8 as ag aS a8 ae Bas 
He | fe’) ge | 2 | ga | Be | Be | BS | Be | gs | Se 
es | 6 | ee |e fee ye [esa | ai 
Wood. « 280 257 64 63 OW 44 15 11 410 375 91 
Concrete . 187 165 9 8 3 3 85 oo 284 231 81 
Brick sae 256 242 10 9 20 24 110 88 403 363 28 
Totaly (eB 664 83 80 81 val 210 154 1097 969 88 









Besides the falling of the tops, a large proportion of the chimneys that suffered this 
loss, as well as a great many that did not, were injured or cracked at the base or some- 
where within the house. Hconomically, the damage below the roof is the most serious, 
as it is difficult to remedy and is a menace to the safety of the building. Some chimneys 
crumbled away entirely. This happened most frequently to those built on the outside 
of the house, in which case they usually fell away from the house, doing little harm. 
This may be considered a point in favor of exterior flues, inasmuch as the wreckage to 
houses due to the chimneys falling through the roofs, as well as the difficulty of repairing 
interior flues, is avoided. On the other hand, the unsupported exterior chimneys show 
a greater tendency to fall. Ash-boxes at the bases. of chimneys weakened them at 
these parts, and made them more liable to injury. Only 12 per cent of the tops of the 
brick chimneys remained standing, the reasons for their standing being generally found 
in the construction of the chimneys themselves. The use of cement and lime instead 
of simply lime mortar, accounts for the standing of many, although the use of cement 
